Examkin

Question

Difficulty: EasyMobile Device Hardware and Display Issues

A field technician is troubleshooting a laptop with a CCFL-backlit LCD screen. The user reports that the screen image is completely dark during normal operation, but when the technician shines a bright flashlight closely onto the glass display, the desktop icons and window outlines are faintly visible. Which of the following components is most likely failing and causing this issue?

  1. The display backlight inverterAnswer
  2. B
    The OLED panel inverter board
  3. C
    The standard full-sized DIMM video memory module
  4. D
    The lithium-ion battery power calibration circuit

Answer

The display backlight inverter is the failing component.
The flashlight test is a standard diagnostic method used on CCFL-backlit LCD displays. If graphics are faintly visible when shining a light onto the glass, the LCD matrix is working properly, but the backlight system is unlit. In traditional CCFL displays, the inverter board converts DC power to AC power to ignite the backlight. A failed inverter results in a dark screen while the LCD image remains intact.

Step-by-Step Solution

1
Analyze the symptom of a dark screen with faint images visible under external light.
Confirm that the LCD matrix itself is operating and rendering graphics correctly.
The ability to faintly view graphics under a flashlight confirms video signal delivery to the liquid crystals.
2
Identify the missing element required for normal visibility on CCFL-backlit screens.
Determine that the internal light source (backlight) is not illuminating.
CCFL backlights require high-voltage AC power provided by a dedicated inverter board.
3
Isolate the most probable root cause.
Conclude that the backlight inverter board has failed.
A failed inverter stops supplying power to the backlight while leaving the LCD panel functional.

Key Concept

CCFL Display Backlight Inverter Troubleshooting
Rate this question

Topics

Mobile Device Hardware and Display Issues

More questions from this topic